Heterojunction light-emitting diode array

Abstract

A light-emitting diode array is fabricated by forming a light-emitting diode heterojunction at the interface between a superlattice layer comprised of alternations of a multiplicity of semiconductor layers that have different energy gaps, and a doped diffusion mixed region having a larger energy gap than that of the superlattice layer which is formed by impurity doping of part of the said superlattice layer. The light-emitting diode array thus formed exhibits low optical crosstalk and good diode uniformity.

What is claimed is: 
     
       1. A heterojunction light-emitting diode array having a plurality of light-emitting diodes positioned in a desired arrangement on a substrate each diode comprising: a superlattice layer on the substrate having alternations of a multiplicity of layers of at least two different semiconductor materials with one of the semiconductor materials having a band gap larger than the other semiconductor materials, and a region of said superlattice layer being doped with an impurity different from that contained in the layers of the superlattice layer to form a diffusion mixed region, the diffusion mixed region forming a light-emitting heterojunction at its interface with the superlattice layer and serving as a window for light generated at the junction, the diffusion mixed region having a larger energy gap than that of the superlattice layer, the superlattice layer having no internal adsorption of the light so as to reduce cross-talk between diodes to thereby improve emission efficiency.   
     
     
       2. The diode array of claim 1 wherein the superlattice layer is n-type and the diffusion mixed region is p-type. 
     
     
       3. The diode array of claim 1 wherein the superlattice layer is undoped, the diffusion mixed region is doped n-type and further including a second superlattice layer having alternating of a multiplicity of layers of at least two different semiconductor materials which are p-type and which is in contact with the said undoped superlattice layer. 
     
     
       4. A heterojunction light-emitting diode array having a plurality of light-emitting diodes positioned in a desired arrangement comprising: a substrate;   a superlattice layer on said substrate, said superlattice layer comprising alternations of a plurality of layers of at least two different semiconductor materials with one of the materials having a band gap larger than the other semiconductor materials; and   a plurality of spaced regions in said superlattice layer containing a doping impurity different from that in the layers of the superlattice layer to form diffusion mixed regions, each diffusion mixed region forming a light-emitting heterojunction with the superlattice layer and having a larger band gap than that of the superlattice layer;   each of the diffusion mixed regions serving as a window for the generated light and the superlattice layer having no internal absorptions of the light so as to reduce cross-talk between the diodes in the array to thereby improve emission efficiency.   
     
     
       5. The diode array of claim 4 in which the diffusion mixed regions are doped p-type. 
     
     
       6. The diode array of claim 5 in which the superlattice layer is doped n-type. 
     
     
       7. The diode array of claim 4 in which the superlattice layer is undoped, the diffusion mixed region is doped p-type and further comprising a second superlattice layer of a plurality of layers of at least two different semiconductor materials which is doped n-type between the undoped superlattice layer and the substrate.